Filtering Apparatus and Filter Element

ABSTRACT

The invention relates to a filtering apparatus comprising a pot-type filter housing ( 10 ), a filter element ( 28 ) that is accommodated therein, a holding mechanism ( 38 ) which is disposed in the filter housing ( 10 ) in order to removably fix the filter element along the longitudinal axis thereof, and a sealing device ( 60 ) that seals between a lid ( 20 ) of the filter housing ( 10 ) and the filter element ( 28 ). The holding mechanism ( 38 ) is provided with cooperating holding elements which are embodied on the interior face of the filter housing ( 10 ) as well as on the filter element ( 28 ). The inventive filtering apparatus dispenses with the need for O-seals that are known in prior art and extend in a radial direction between the filter element and the filter head as a housing lid because the sealing device ( 60 ) encompasses at least one sealing edge ( 62 ) or sealing surface which is placed parallel to the longitudinal axis in a radial direction and seals under the effect of the pressure applied thereto by the holding mechanism ( 38 ). The invention further relates to a filter element that is to be used in such a filtering apparatus.

The invention relates to a filtering apparatus having a cup-like filter housing, a filter element which can be held therein and a holding means which is located in the filter housing for detachable fixing of the filter element along its longitudinal axis and which has holding elements which interact with one another and which are formed on the inside of the filter housing and on the filter element, and with a sealing means which effects sealing between the housing cover of the filter housing and the filter element. The invention furthermore relates to a filter element designed for the filter device.

Filter devices for holding filter elements are readily available commercially in a host of embodiments. A not insignificant portion of production costs in these filter devices is for making the holding means for detachable fixing of the filter element within the pertinent housing and for the sealing means for sealing the interior of the filter element relative to the filter housing.

In the filter device described in EP 0891 214 B1, the holding means has a spring configuration of two compression springs which act against one another; by their resulting spring force an end piece, which is located on the filter element and which acts as a sealing and holding element, is pushed onto a housing-side holding element which forms a fluid connecting branch formed on the head of the filter housing by a connecting piece which extends into the support pipe of the filter element. The comparatively complex design of the known holding means leads to high production costs and the known solution is less easy to install, in that the filter element can slip unintentionally off the connecting branch or can tilt at this location when put in place; this leads to an adverse effect on the sealing action of the sealing means. In the known solution, the sealing means has an O-ring, preferably of rubber material, which is fixed in the radial internal recess within the end cap of the filter element and in this way radially effects sealing relative to the outer peripheral side of the fluid connecting branch of the housing cover or of filter head. This known sealing means with an O-ring is not suited for all fluid media, for example not for all hydraulic liquids, poorly flammable liquids, corrosive media and for special biodegradable liquids. Depending on the chemical structure of the respective medium, a long-lasting sealing function cannot be ensured.

The subject matter of DE-U-299 22 488 is a liquid filter which is easy to install, with a cup-like filter housing and with a removable cover which closes the filter housing, and with an interchangeable filter insert which has its own filter surface, the filter insert being detachably connected to the cover as the filter head of the housing. Furthermore, the known solution has a support mandrel which extends into the filter insert as a connecting branch of a holding means, in the filter housing connecting and holding means which are referred to as an adapter being provided for the support mandrel, which connecting and holding means are designed as holding elements in the form of retaining fingers. In the known solution the support mandrel is detachably held in the filter insert, a first installation module having the cover, the filter insert and the support mandrel and a second installation module having the filter housing and adapter with the retaining fingers. During installation of the two installation modules then the adapter is securely connected to the support mandrel and when the filter insert is replaced, the support mandrel remains in the filter housing. In this respect installation problems (slippage, tilting) can also arise when the filter element has to be pushed onto the support mandrel, for example when the filter is being replaced on site, with the disadvantageous consequence that the sealing action of the sealing means is adversely affected, which in turn formed from an O-ring in the radial direction effects support between the support mandrel of the filter housing and the inner peripheral side of the filter element. Although in addition the support mandrel as a component of the holding means in the longitudinal axial direction parallel to the longitudinal axis of the filter element on its lower base part in a receiving groove has another gasket which is not subject to any further mechanical stress, in any case, as described above the sealing action of the sealing means between the filter element and support mandrel as a housing part is adversely affected.

EP 1 287 871 A1 discloses a filter device with the features of the preamble of claim 1. The holding elements in the known filter device are a receiver located on the filter housing with an undercut forming at least one catch surface and on one end of the filter element, projecting, resilient retaining fingers with catch projections which form a detachable snap connection by locking to the catch surface of the receiver. In this way installation and replacement of filter elements can be done by simple locking and releasing by means of the snap connection, it being sufficient to move the pertinent filter element axially in the filter housing in the direction to the cup bottom until the snap connection snaps in, or for dismounting from the cup-shaped housing, to simply pull it out. With the known solution, in terms of a means of non-interchangeability, the result is that only filter elements designed especially for the filter device can be used for assuming a function and for example no other components which are formed optionally as aftermarket elements could endanger the safe use of the filter device.

On the opposite end of the filter element with parts of the holding means, the end cap of the filter element has a fluid connecting branch which can be slipped onto a connecting branch part in the housing cover or filter head. The sealing means is in turn an O-ring which extends radially between the connection parts of the cover part and filter element. In this respect the above described disadvantages also apply to the known filter device according to the indicated European patent.

The object of this invention, on the basis of the most similar prior art while retaining its advantages, specifically guaranteeing a reliable connection of the filter element within the filter housing by way of the holding means, is to further improve it such that it is characterized by a structurally especially simple design, accordingly has low production costs and is easy to install, and has good sealing action, also relative to corrosive media. Furthermore, the object of the invention is to make available a filter element suitable for this filter device. These objects are achieved by a filter device with the features of claim 1 in its entirety and a filter element with the features of claim 8.

In that, as specified in the characterizing part of claim 1, the sealing means has at least one sealing edge or sealing surface, which located in the axial direction parallel to the longitudinal axis seals under the influence of the pressure applied thereto by the holding means, it is possible to abandon conventional O-rings which extend between the filter element and the filter head as the housing cover in the radial direction. Nor does the sealing means have to be made from rubber materials, as in the known solutions, and is accordingly suitable for any type of fluid to be filtered, even corrosive media. Depending on the medium to be filtered in the form of a fluid, the sealing means can be stipulated to be suitably resistant in terms of its material selection. Damage to the sealing means in the various installation processes can also for the most part be avoided, even if the filter element were to be placed obliquely on parts of the holding means so as to cause tilting. In this way long lasting operation can be ensured by way of the sealing means.

In that, as specified in the characterizing part of claim 8, for use in a filter device on at least one end of the filter element an end cap is placed which on its side facing away from the filter element has a sealing means which, designed as a closed ring with a sealing edge or sealing surface, is arranged in the direction parallel to the longitudinal axis of the filter element, the sealing means is located outside of the actual holding means and damage to the sealing means is thus avoided when the filter element is fixed by way of the holding means within the filter housing. By preference provision can be made such that the sealing means with its sealing edge is an integral component of the filter element-end cap, and for the end cap configuration, and accordingly for the sealing means, a plastic or steel material which is resistant with respect to corrosive media can be preferably selected. But fundamentally it is also possible to detachably integrate the sealing means into a receiving means, for example in the form of a receiving groove within the end cap. But it is essential to all the indicated solutions that via a force means which can be formed from parts of the holding means, pressing of the sealing means with its sealing edge takes place in the axial direction between the face-side end of the filter element and the housing cover or filter head. In this connection it is also possible to additionally or alternatively arrange the sealing means on the filter head or housing cover; the sealing means then works axially in the direction of the face-side end of the filter element.

In one preferred embodiment of the filter device as claimed in the invention, the holding means consists of an outer thread and an inner thread corresponding to it, the holding elements being formed from the pertinent turns of the outer and inner thread so that it is possible to connect the filter element to housing parts of the filter housing to carry fluid by a screwing-on process which is simple to carry out, or to detach them again from one another by an unscrewing process. In this connection it is unimportant whether the outer thread is assigned to the filter housing or the filter element. Based on the thread characteristic of the holding means solution, the indicated solutions involving pushing onto the connecting branch in the filter housing can be abandoned; this facilitates installation processes. In particular, the filter element does not unintentionally slip off the connecting branch nor does it tilt on the pertinent connecting piece configuration. This thread solution forms the force means which makes it possible to brace the sealing means with its sealing edge or sealing surface against parts of the filter housing, especially in the form of a cover part (filter head) and/or against the end cap of the filter element, the pressing of the sealing edge or sealing surface of the sealing means also being determined essentially by its resilience and flexibility.

With the solution as claimed in the invention, only one specific type of filter elements can ever be inserted into the filter housing which filter elements being specifically prepared accordingly for the indicated threaded connection approach. Thus, the insertion of aftermarket components can be avoided, as such replacement parts which, in addition to their fundamentally poor quality, also as a result of their less specific adaptation to the intended filter housing entail tightness problems on the fluid connecting points.

In one preferred embodiment of the filter device as claimed in the invention, it is provided that the outer thread is located on the end cap of the filter element and concentrically to it and that the pertinent inner thread is integrated in the filter housing. Furthermore, the outer thread comprises preferably a fluid passage site in the filter element and the filter housing is made in several parts, the inner thread being held in the housing cover (filter head) of the filter housing and encompassing another fluid passage site. In this way, the filter element can be inserted by way of a classical receiver in the filter housing and by a snap-on or screw-on process of the cover on the filter housing the fluid-carrying connection from the hydraulic circuit to the filter element is established by way of the indicated thread and threaded sections. Preferably, the connecting branch of the filter element on the base side is encompassed by the sealing means.

Other advantageous embodiments of the invention are the subject matter of the other dependent claims.

The filter device as claimed in the invention in addition to the assigned filter element will be detailed below using one embodiment as shown in the drawings. The figures are schematic and not to scale.

FIG. 1 shows in a perspective side view part of the filter device as claimed in the invention, with the cover part as the filter head screwed off;

FIG. 2 shows in a perspective bottom view the cover part of the filter housing as shown in FIG. 1;

FIG. 3 shows the top end of the filter device with the filter element inserted and the cover part in place on the otherwise cup-like filter housing.

A filter housing 10 in the form of a cup which is rotationally symmetrical in its outline to the longitudinal axis 12 has one open top end 14 and a closed bottom (not shown). On the top end 14 there is a peripheral catch groove 16 which in the form of a snap connection can be engaged by a catch overlap of the cover part 20 of the filter housing 10, when the cover part 20 is placed on the top end 14 of the filter housing 10 by means of a rotary or snap motion. This snap and catch connection for the housing cover 20 with the filter housing 10 is shown especially in FIG. 3. But it would also be possible, as shown in FIG. 1, instead of a catch groove 16 to provide a peripheral elevation 22 and to provide it with an external threaded segment (not shown) in order in this way to screw on the housing cover 20 by means of an internal threaded segment which is not shown. But in both cases, as shown in FIG. 1, in the direction of the top end 14 there is a projecting, peripheral sealing lug 24 which at the top borders a sealing channel 26 which can house a sealing means which is not shown, for example in the form of an O-ring or the like. But optionally sealing by way of the projecting sealing lug 24 without other sealing means is sufficient here.

The cup-like housing 10 is designed to hold a filter element 28 in the form of a filter cartridge which conventionally has a circular-cylindrical inner support pipe with fluid passages, which is surrounded by the filter material 30. In this embodiment the filter element 28 should have a lower end which is assigned to the bottom of the filter housing and which is closed by a plastic end cap which also forms an enclosure for the facing end edge of the filter material 30.

This end cap which is not detailed can be compression molded with the support pipe in one piece from plastic. This lower end cap is closed, that is, made fluid-tight, and need only to be inserted within the filter housing 10 in the direction of its bottom, while maintaining an axial distance. But it would also be conceivable here to use conventional holding and receiving means, as are known in the prior art. On its end assigned to the upper end 14 of the filter housing 10, the filter material 30 together with the support pipe is lengthened by a preferably plastic, compression-molded head cap or end cap 32 which likewise forms an edge enclosure 34 for the bordering edge of the filter material 30 and a connecting branch 36.

This connecting branch 36 is part of the holding means which is designated as a whole as 38 and which has an outer thread 40 along the connecting branch 36. Corresponding thereto in the housing cover 20, set back opposite its free edge 42, there is an inner thread 44 which is aligned in the direction of the longitudinal axis 12 of the filter device. The actual holding elements 46 of the holding means 38 consist of the pertinent thread turns of the outer thread 40 and inner thread 44.

As FIG. 1 and FIG. 3 furthermore show, the outer thread 40 on the end cap 32, which is also referred to as the element cover, is arranged concentrically to it, the pertinent inner thread 44 being integrated in the bottom part of the housing cover 20. The connecting branch 36 and accordingly the outer thread 40 concentrically encompass a fluid passage site 48 in the filter element 28. The inner thread 44 integrated in the housing cover 20 borders another fluid passage site 50, and the assignable inner threaded segment can be a component of an insert sleeve 52 (compare FIG. 2) which can be inserted into an assignable hole in the housing cover 20 and can also consist of a plastic material in the form of a compression or clamping sleeve. In addition to the other fluid passage site 50, the cover part 20 has a fluid inlet site 54 for the fouled fluid.

Inflowing, fouled fluid, especially hydraulic medium, then travels with the housing cover 20 in place on the remaining filter housing 10 via the fluid inlet site 54 into the interior of the filter element 10 and in this way flows through the filter element 28 from outside to inside. The dirt to be removed then remains in the filter material 30 of the filter element 28 and the cleaned fluid which has then collected within the support pipe leaves the filter housing 10 with the housing cover 20 via the fluid passage site 48 and the other fluid passage site 50. It goes without saying that for its filter function the filter device can be connected to a hydraulic circuit (not shown) via connecting points 56.

For an economical sealing means, it has been found to be advantageous to make the thread turns of the outer thread 40 and the assignable inner thread 44 as so-called round threads. Furthermore, to ensure a stiff configuration, the connecting branch 36 is kept as small in diameter as in overall height; in particular in diameter it is kept several times smaller than the outside diameter of the end caps 32. In order to provide favorable flow conditions, moreover the free end of the connecting branch 36 is provided on the inner peripheral side with a funnel-shaped curvature 58. Furthermore, the connecting branch 36 on its base-side transition point to the end cap 32 is surrounded with a concentrically running sealing means 60. As FIG. 3 shows in particular, the sealing means 60 is made triangular in cross section and seals with a tapering sealing edge 62 in the direction of the bottom of the housing cover 20 if it is placed on the remaining filter housing 10 (compare FIG. 3).

This sealing edge 62 can be slightly compressed if, when the housing cover 20 is fixed, it is drawn by way of the holding elements 46 in the form of thread turns in the direction of the filter element 28 and of the filter housing 10. The holding means 38 therefore yields a positive and nonpositive fluid connection between the filter element 28 and the housing cover 20, the sealing means 60 being nonpositively compressed in contact with the housing cover 20. Because the sealing means 60 with the sealing edge 62 is located on the end cap 32 with the threaded connecting branch 36, in this way sealing is effected between the filter element 28 and the filter head in the form of the housing cover 20. Thus, other sensitive seal materials, for example of rubber, which are intended to otherwise ensure the sealing function in the manner of an O-ring, are omitted. Since the sealing means 60 is made of the same material as the end cap 32 and is especially an integral component of it, the sealing means 60 is thus suited for all hydraulic liquids, poorly flammable liquids, corrosive media and for all biodegradable liquids; media for which conventional sealing means, especially of rubber material, can no longer guarantee a sealing function over a long interval.

Since the filter element 28 is held in a defined manner by way of the threaded segment in the housing cover 20 and accordingly in the filter head, in mounting and dismounting processes, for example to replace a used filter element 28 by a new one, it cannot, as in the prior art, lead to the connecting branch 36 slipping off unintentionally. Rather a precisely manageable contact situation prevails and when the housing cover 20 is locked on the filter housing side 10, it is ensured that a fluid-carrying connection is also produced within the filter device. Preferably, the filter element is first screwed into the cover part for an insertion process and then it is locked to the filter housing 19. Moreover, for the filter device as claimed in the invention a defined filter element 28 is necessary in terms of the connection construction, so that it is not possible to insert possible aftermarket components into the existing filter device housing which could otherwise endanger the operation of the filter device as a result of tightness problems.

The sealing means 60 is selected in terms of its overall height such that on the base-side outlet of the threaded segment of the outer thread 40 it projects as a round thread by half a thread turn. But it is also possible, instead of a round thread, to use another metric thread. Furthermore, several gaskets—also in another geometrical configuration—in a concentric arrangement and optionally at a different sealing height can encompass the connecting branch 36. Furthermore, it is still within the scope of the invention to interchange the arrangement of the outer and inner thread so that then the housing 20 has the outer thread and the end cap 32 of the filter element 28 has the inner thread 44 (design not shown). In addition to the described force means in the form of threaded segments of the holding means, it is also possible to brace nonpositively, for example by way of a spring element in the form of a compression spring, comparably to the solution as shown in FIG. 5 of EP 0 891 214 B1, against the connecting branch in the filter head or cover part of the filter housing and in this way to apply a sealing force to the sealing means in the axial direction. 

1. Filtering apparatus with a cup-like filter housing (10), a filter element (28) which can be held therein and a holding means (38) which is located in the filter housing (10) for detachable fixing of the filter element along its longitudinal axis (12) and which has holding elements (46) which interact with one another and which are formed on the inside of the filter housing (10) and on the filter element (28), and with a sealing means (60) which effects sealing between the housing cover (20) of the filter housing (10) and the filter element (28), characterized in that the sealing means (60) has at least one sealing edge (62) or sealing surface, which located in the axial direction parallel to the longitudinal axis (12) seals under the influence of the pressure applied thereto by the holding means (38).
 2. The filter device as claimed in claim 1, wherein the holding means (38) consists of an outer thread (40) and an inner thread (44) corresponding to it and wherein the holding elements (46) are formed from the pertinent turns of the outer (40) and inner thread (44).
 3. The filter device as claimed in claim 1, wherein the outer thread (40) is located on the end cap (32) and concentrically to it and wherein the pertinent inner thread (44) is integrated in the filter housing (10).
 4. The filter device as claimed in claim 3, wherein the outer thread (40) encompasses a fluid passage site (48) in the filter element (28).
 5. The filter device as claimed in claim 3, wherein the filter housing (10) is made in several parts and wherein the inner thread (44) is held in the housing cover (20) of the filter housing (10) and encompasses another fluid passage site (50).
 6. The filter device as claimed in claim 5, wherein the sealing means (60) encompasses the holding means (38) at the transition point to the filter element (28).
 7. The filter device as claimed in claim 1, wherein the thread turns (46) are made as a round thread.
 8. Filter element for use in a filter device as claimed in claim 1, wherein on at least one end of the filter element (28) an end cap (32) is placed which on its side facing away from the filter element (28) has a sealing means (60) which, in the form of a closed ring with a sealing edge (62) or sealing surface, is arranged in the direction parallel to the longitudinal axis (12) of the filter element (28).
 9. The filter element as claimed in claim 8, wherein the outer thread (40) of the end cap (32) extends along the connecting branch (36) which encompasses one fluid passage site (48).
 10. The filter element as claimed in claim 9, wherein the connecting branch (36) on the base side is encompassed by the sealing means (60). 